Which rust killer is best: Wattyl or White knight?

[Cranswick]

Hi l have some galvanized steel posts under my house with some light surface rust, l want to first apply a rust killer/ converter before l paint them with a primer, which is the best rust converter product to use between these two " white knight rust guard converter" or Wattyl Killrust Rust Eeter" are both these suitable for galvanized steel and will not harm the galvanized surface? l dont want to use rannex rustbuster because they recommend not for use on galvanized steel . Which one of these two is most effective or are both the same? and are both OK for glavanized steel

[MitchellMc]

Hi @Cranswick,

As we don't stock the Wattyl Killrust, I don't have experience using it, though I do know the White Knight Rust Guard works perfectly well on lightly rusted steel, wrought iron and other ferrous metals. It's always best to try and knock off as much of the existing rust as possible before applying the convertor. I recommend using a wire brush, whether manual or attached to a drill or angle grinder. Always remember your PPE, including safety glasses.

If your galvanised surface has rusted, that indicates that the galvanised coating has been compromised. You should really sand the area back to remove the rust and expose the bare steel. You can then convert the bare steel or simply apply new gal coating.

Please let me know if you have any questions.

Mitchell

[Cranswick]

Thanks , after l sand the steel would this be a good rust converter to use  "Dy-Mark 350g MetalPro Rust Converter" , would that be just as effective as other rust converters you stock,   if l apply that and then after that l apply a coat of "  Dy-Mark 1L MetalPro Zinc Gal Primer" , would applying those two products be an effective treatment. If l am not able to sand off all the rust and there is still some rust left underneath the coating of gal paint  will it most likely no longer be able to grow or get worse

[MitchellMc]

It's best to try to remove all traces of rust before applying the gal coating to the bare steel @Cranswick. You can use a combination of sanding and a wirewheel. 

The Dy-Mark 1L MetalPro Zinc Gal Primer is designed to go onto bare steel, not a rust converter. If trace amounts of rust remain, sealing over them will halt the corrosion process by preventing oxygen and moisture from accessing the area.

Mitchell

[Cranswick]

After l sand Should l apply a rust conveter first to kill any remaining rust before l apply the MetalPro Zinc Gal Primer? or skip the rust converter and just paint it with the Zinc primer?   if so what is the best rust converter that you stock to use that will be most effective in killing the remaining rust ? is the metal pro rust converter below any good or is rannex rustbuster better 

[MitchellMc]

The Dy-Mark 1L MetalPro Zinc Gal Primer must be applied over bare steel @Cranswick. You can not apply it over a rust convertor. If you want to apply a rust converter like the Dy-Mark 350g MetalPro Rust Converter, you can only paint over the top of it, not use the galvanised coating.

Dy-Mark MetalPro RUST CONVERTER is a tannic acid based rust converter specially formulated for the treatment of rusted surfaces. In one easy step, Metalpro Rust Converter chemically reacts with the rust to form a black inert organic compound that binds to the surface and provides a barrier by sealing out moisture for effective rust protection. Suitable for use under most paint systems. For superior protection it is recommended to overcoat with Dy-Mark MetalPro Primer and then with Dy-Mark MetalPro Quick Dry range of topcoat colours within 3 months of surface preparation with MetalPro Rust Converter.

Mitchell

[Cranswick]

THanks so do you think l dont need to use a rust converter at all,  just sand the rust off the steel and then paint the steel with MetalPro Zinc Gal Primer, and if theres any rust left it wont be able to get worse because it will be cut off from oxygen and moisture. is that the best way to go rather then using a rust converter like rannex . After l sand the steel l would then need to clean it before painting the zinc primer, what is the best product to clean it with

[MitchellMc]

If it's just light surface rust @Cranswick, I'd give it a quick sand, hit it with a wire wheel, and then apply the gal primer over the top. I do not think you need to use the rust converter. No need to stress about a few specks of rust here and there. Once the gal coating is on there, it will inhibit the corrosion process.

To clean the steel before applying the gal primer coating, I'd just brush/wipe it down. You could use acetone, but personally, I wouldn't bother.

Mitchell